Field of the Invention
The present invention relates to a wireless communication system, and more particularly to a method for transmitting and receiving automatic repeat request (ARQ) feedback information in a wireless communication system.
Discussion of the Related Art
First, a conventional Medium Access Control (MAC) Protocol Data Unit (PDU) format and a generic MAC header (GMH) format will hereinafter be described with reference to FIGS. 1 and 2.
FIG. 1 is a MAC PDU format according to the related art. FIG. 2 is a generic MAC header according to the related art.
Referring to FIG. 1, the MAC PDU may include a generic MAC header, a payload, and a Cyclic Redundancy Check (CRC).
The generic MAC header includes control information therein. The payload includes actual information to the exclusion of various operation and control headers. The CRC is used to check the presence or absence of an error. In more detail, the CRC is obtained when the result extracted from a polynomial expression is added to data to be transmitted, such that a transmitter transmits the resultant data as the CRC so as to perform an error check.
Referring to FIG. 2, a Header Type (HT) field represents a header type. The generic MAC header according to the related art is classified into two header types according to the presence or absence of payload. The HT field represents a header type of a corresponding general MAC header. If the generic MAC header has a payload, the HT field is set to ‘0’. In contrast, if the generic MAC header does not have a payload, the HT field is set to ‘1’.
The generic MAC header having no payload is used to transmit signaling information. The signaling header type defined in the related art is classified into a MAC signaling header type 1 and a MAC signaling header type 2. The MAC signaling header type 1 includes a bandwidth (BW) request, a BR (Bandwidth Request) and UL Tx (Uplink Transmission) power report, a Carrier to Interference Noise Ratio (CINR) report, a physical channel report, and the like. The MAC signaling header type 2 includes a feedback header and the like.
‘Type’ field represents whether MAC subheaders are transmitted or not. According to the conventional art, 6 MAC subheaders are defined, the Type field is composed of 6 bits, and each of the 6 bits represents the presence or absence of each subheader.
Six MAC subheaders defined in the related art are a fragmentation subheader (FSH), a grant management subheader (GMSH), a packing subheader (PSH), an Automatic Repeat Request (ARQ) feedback, a mesh subheader, and a Fast-feedback allocation subheader (FFSH).
Next, the ARQ feedback method according to the related art will hereinafter be described in detail.
In the conventional art, if a receiver receives an ARQ-enabled PDU, it transmits an acknowledgement (ACK) message or a negative acknowledgement (NACK) message through ARQ feedback Information Elements (IEs). The receiver transmits the ACK or NACK message for all the transmitted ARQ-enabled PDUs according to an established ARQ feedback type. The ARQ feedback is transmitted as a payload format by the ARQ feedback IE, the transmission or non-transmission of the ARQ feedback payload is indicated by a fourth bit of the Type field of the generic MAC header. In the case where the ARQ feedback IE is packed with other MAC SDUs, it is located at the first one from among the packed SDUs or SDU fragments.
However, according to an Institute of Electrical and Electronics Engineers (IEEE) 802.16m system that is being standardized, a transmitter can transmit an ARQ feedback polling request to a receiver. In the case where the receiver does not receive the ARQ feedback polling request from the transmitter or does not receive an ARQ block from the transmitter during a predetermined interval, it transmits the ARQ feedback to the transmitter.
In this case, if a mobile station serves as the receiver, i.e., when the mobile station transmits ARQ feedback indicating whether or not downlink data is successfully received to a base station, a method for enabling the base station to efficiently allocate resources for ARQ feedback transmission to the mobile station is strongly needed.